1. Field of the Invention
The present invention relates generally to concrete, and particularly to a synthetic aggregate for use in concrete, the aggregate being a composite of recycled plastic with a filler encapsulated in the plastic.
2. Description of the Related Art
Concrete is one of the most important and frequently used materials in civil engineering, such as in high-low buildings, bridges, infrastructure and environmental protection facilities. Concrete is a composition of an aggregate and a binder substance. The binder substance and the aggregate are combined by a moistening agent to allow the binder substance to link with aggregate particles and form a solid block. Generally the aggregate or aggregates make up about 60% to 70% of the total concrete volume. Since the properties of the aggregates used in concrete significantly impact the quality of the concrete, the selection and the proportion of the aggregates is very important and should be given careful attention. For example, air-cooled sage is used to replace coarse aggregate materials and fly ash is used to replace fine aggregate materials. Furthermore, aggregates such as silica fume and rice husk ash have been used as supplementary cementing materials. Natural aggregates, such as those mentioned, give concrete certain physical, chemical, and mechanical properties.
However, as a result of environmental concerns, there has been a growing trend for the use of recycled plastic waste as artificial aggregate instead of natural aggregate in the production of concrete. Over the last 30 years, worldwide production of plastic grew by more than 500%. Current annual global production is estimated at over 100 million tons and is expected to increase by 3% a year. In the U.K., 7% of plastics are recycled each year, which is a small quantity when compared to the 275 million tons of natural aggregate used in concrete applications. About 80% of the plastic wastes are either left in stockpiles, as landfill material, or is illegally dumped. Most importantly, much of the non-decaying wastes will remain in the environment for hundreds, perhaps thousands of years. The non-decaying waste will not only cause a waste disposal crisis, but also contribute to significant environmental problems. As such, the possibility of using a synthetic aggregate, such as a recycled plastic as aggregate, instead of a natural aggregate in concrete has received increasing attention in recent years as a solution to the escalating solid waste problem.
However, currently, synthetic aggregate, such as recycled plastic aggregate, does not allow for the same physical, chemical, or even mechanical properties of natural aggregates.
Thus, a synthetic aggregate for use in concrete solving the aforementioned problems is desired.